1. Field of the Invention
The present invention relates to a method of determining inaccuracy information in positioning a data model of virtual information in an augmented reality system. In doing so, the data model is projected to the image plane of a display device and mixed or blended with visual impressions of a real environment. In addition thereto, the present invention relates to a corresponding system for determining inaccuracy information in positioning a data model of virtual information in an augmented reality system.
2. Description of the Related Art
So-called augmented reality systems are commonly known. These permit the superposition of computer-generated virtual information with visual impressions of the real environment. To this end, the visual impressions of the real world are mixed with virtual information, e.g. by means of semi-transmissive data glasses worn on the head of a user. The blending-in of virtual information or objects can be effected in context-dependent manner, i.e. matched to and derived from the respective real environment viewed. As virtual information, it is basically possible to use any type of data, such as texts, images etc. The real environment is detected e.g. with the aid of a camera carried on the head of the user. An example of a possible application of an augmented reality system in a production environment is shown in publication DE 101 28 015 A1. The latter describes an augmented reality system for planning altered production environments in the field of production industry.
Furthermore, there are known measuring methods in an augmented reality system. In this regard, e.g. statements on absolute positions of virtual objects are generated in the camera view. In addition thereto, statements on relative positions of virtual objects e.g. with respect to a real object may be generated in the camera view. The structures, advantageously points or areas, for which a statement is to be made, are chosen manually. This is effected e.g. by selection of the desired structure by the user in the camera view, advantageously via mouse clicks to the corresponding locations in the image, by indication of corresponding three-dimensional coordinates or by definition of virtual planes. In case of real objects, the reference for this selection are the 2D projections of the same in the image, and in case of virtual objects, the three-dimensional representation of the same having the real environment superposed thereon.
The accuracy of the measurement statements is based on the deviation between an actual position and a reference or ideal position of virtual objects in the camera view. In this respect, the reference position corresponds to the position that would be taken by the virtual object in a virtual world that is perfectly computed, i.e. is an accurate image of the real world. The reference position of the virtual object thus presents itself as the position that would be taken by the real counterpart of the same in the camera image. A deviation of the actual position is caused by factors afflicted with inaccuracies.
The German Industrial Standard (“DIN”) ENV 13005, “Leitfaden zur Angabe der Unsicherheit beim Messen” (“Guideline for indicating of uncertainty in measurement”), German version ENV 13005, 1999, represents a guideline with the purpose of recommending an internationally uniform procedure for determining and indicating measurement uncertainties. This DIN standard relates to the indication and determination of uncertainty of measurement results in the general field of technology. Uncertainty in this regard is understood as the parameter associated with the measurement result, which defines the variance of the values that may be reasonably associated with the measured. The parameter may be a standard deviation of a range having a fixed level of confidence. More details in this regard can be found in the afore-mentioned DIN standard.
Due to the afore-mentioned inaccuracies in an augmented reality system, only inaccurate positioning of the virtual object is possible in general. Due to the fact that the exact deviation of the actual position from the reference position of the virtual object is unknown, a measurement statement can be made in the form of an estimate only, which however satisfies the requirements of the DIN standard in insufficient manner only. The systems known from the prior art in this regard involve the disadvantage that, for such measurements, it is so far not possible to make statements on the uncertainty of the result. If the measurement result is just an estimation of the actual value, the indication of the measurement result is complete only if it is accompanied by the indication of the measurement uncertainty of the estimated value, as specified in the DIN standard.
Ronald T. Azuma: “A Survey of Augmented Reality”, Hughes Research Laboratories (1995), pages 1 to 40, reveals a survey on the subject of augmented reality as well as augmented reality systems, discussing also tracking and registration techniques by means of which a data model of virtual information is projected on the image plane of a display device. Furthermore, said documents describes static and dynamic error sources resulting in registration errors in augmented reality systems. Georg Klein, Tom Drummond: “Robust Visual Tracking for Non-Instrumented Augmented Reality”, ISMAR '3, 2003, original pages 113 to 122, pages 1 to 10, also is concerned with registration errors in augmented reality systems, with this document dealing in particular with the compensation of errors caused by motion blur in motion models. In said document, the correction of the errors relates in particular to the superposition of a (virtual) re-projection of an object with the actual object in the image plane. The correction in this regard aims at keeping the two-dimensional registration error low and at optically optimizing the superposition.